this.addClass("Xmlhttp", "@mozilla.org/xmlextras/xmlhttprequest;1", [], "open");
this.addClass("XPathEvaluator", "@mozilla.org/dom/xpath-evaluator;1", "nsIDOMXPathEvaluator");
this.addClass("XMLDocument", "@mozilla.org/xml/xml-document;1", ["nsIDOMXMLDocument", "nsIDOMNodeSelector"]);
this.addClass("Xmlhttp", "@mozilla.org/xmlextras/xmlhttprequest;1", [], "open");
this.addClass("XPathEvaluator", "@mozilla.org/dom/xpath-evaluator;1", "nsIDOMXPathEvaluator");
this.addClass("XMLDocument", "@mozilla.org/xml/xml-document;1", ["nsIDOMXMLDocument", "nsIDOMNodeSelector"]);